The United Steelworkers union (USW) issued notices of a possible strike to several US refineries on Friday night as the current contract was set to expire at 12:01 am on Sunday, sources familiar with the notices said. KFDM-TV in Beaumont, Texas, reported on Saturday morning that the Exxon Mobil Corp refinery in Beaumont had received one of the strike notices. An Exxon spokesman did not have information immediately available about a strike notice. A USW representative was not immediately available to discuss the matter.